virtio_console uses a small DMA buffer for control requests. Move
that buffer into heap memory.
Doing virtio DMA on the stack is normally okay on non-DMA-API virtio
systems (which is currently most of them), but it breaks completely
if the stack is virtually mapped.
Tested by typing both directions using picocom aimed at /dev/hvc0.
Signed-off-by: Andy Lutomirski <luto at kernel.org>
---
Hi all-
This is currently broken in tip:x86/asm. If you (Amit) like this patch,
would it make sense for Ingo to add it to -tip?
Thanks,
Andy
drivers/char/virtio_console.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index d2406fe25533..5da47e26a012 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -165,6 +165,12 @@ struct ports_device {
*/
struct virtqueue *c_ivq, *c_ovq;
+ /*
+ * A control packet buffer for guest->host requests, protected
+ * by c_ovq_lock.
+ */
+ struct virtio_console_control cpkt;
+
/* Array of per-port IO virtqueues */
struct virtqueue **in_vqs, **out_vqs;
@@ -560,28 +566,29 @@ static ssize_t __send_control_msg(struct ports_device
*portdev, u32 port_id,
unsigned int event, unsigned int value)
{
struct scatterlist sg[1];
- struct virtio_console_control cpkt;
struct virtqueue *vq;
unsigned int len;
if (!use_multiport(portdev))
return 0;
- cpkt.id = cpu_to_virtio32(portdev->vdev, port_id);
- cpkt.event = cpu_to_virtio16(portdev->vdev, event);
- cpkt.value = cpu_to_virtio16(portdev->vdev, value);
-
vq = portdev->c_ovq;
- sg_init_one(sg, &cpkt, sizeof(cpkt));
-
spin_lock(&portdev->c_ovq_lock);
- if (virtqueue_add_outbuf(vq, sg, 1, &cpkt, GFP_ATOMIC) == 0) {
+
+ portdev->cpkt.id = cpu_to_virtio32(portdev->vdev, port_id);
+ portdev->cpkt.event = cpu_to_virtio16(portdev->vdev, event);
+ portdev->cpkt.value = cpu_to_virtio16(portdev->vdev, value);
+
+ sg_init_one(sg, &portdev->cpkt, sizeof(struct virtio_console_control));
+
+ if (virtqueue_add_outbuf(vq, sg, 1, &portdev->cpkt, GFP_ATOMIC) == 0) {
virtqueue_kick(vq);
while (!virtqueue_get_buf(vq, &len)
&& !virtqueue_is_broken(vq))
cpu_relax();
}
+
spin_unlock(&portdev->c_ovq_lock);
return 0;
}
--
2.7.4
